Mars Water: Much Ado About Very Little

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In the search for life elsewhere in the universe, liquid water is the Holy Grail. Liquid water is absolutely essential for life, so in the estimation of many scientists, the presence of liquid water on another planet at the very least opens the door to the possibility of life there. While water is a common substance in the universe, the earth is the only place that we know for certain where liquid water exists. That is, until Monday, September 28, 2015, when NASA officials announced in a press conference the discovery of evidence of liquid water on the surface of Mars. Or, maybe not.

In a brief paper published the same day, a team of eight scientists claimed spectral evidence for hydrated salts in recurring slope lineae (RSL) on Mars. What are RSL? They are narrow, dark streaks on some slopes that appear in the Martian spring, intensify in summer, and then fade in autumn. Being very thin, RSL show up only in the highest resolution images of the Martian surface, such as those supplied by the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (RSO).

RSL have been known for a few years. The most popular explanation for them has been that they are deposits left behind by brine solutions. That is, they are the result of the flow of liquid water, but there was no evidence of this. A major problem is that liquid water normally cannot exist on the Martian surface. The air pressure and temperature are so low on Mars that any liquid water rapidly boils or freezes. However, the presence of certain salts can simultaneously lower the temperature at which water freezes and raise the temperature at which water boils. With an increase in the temperature range at which liquid water can exist even in the very low pressure of the Martian atmosphere, it may be possible for minute amounts of liquid water to exist on the surface of Mars. Hydrated salts incorporate liquid water into their chemical structure.

Also aboard the RSO orbiting Mars is the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), which the team used to take infrared (IR) spectra of several regions with RSL. In four of the regions where RSL have been seen, the team found IR spectral features that are consistent with magnesium perchlorate, magnesium chlorate, and sodium perchlorate. At least at one site, the spectral features were stronger when the RSL were most pronounced. Keep in mind that while the IR spectral features are consistent with certain hydrated salts, this is not definitive proof that that is actually what is present—other substances could account for these spectral features as well. While the data are not direct evidence for liquid water, it is indirect evidence for liquid water. So, for now many scientists are convinced that at least small traces of liquid water seasonally exist on the Martian surface.

Where would this water come from? There are at least three suggestions, though each one has difficulties. One possibility is the melting of surface or subsurface ice, but that would seem very unlikely in the equatorial regions where some RSL have been found. A second possibility is discharge from local aquifers, but that seems unlikely for RSL extending to the tops of local peaks. A third possibility, the one apparently favored by the authors of the study, is deliquescence, the absorption of water vapor from the atmosphere, but it is unclear if there is enough water vapor in the Martian atmosphere to do this. The authors of the paper pointed out that deliquescence of hygroscopic salts provides the only known refuge for active microbial communities in the driest portion of the Atacama Desert. This is an obvious pitch for the possibility of bacterial life on Mars today.

In many respects, this is not a new story. We have known for decades that water once was abundant on the Martian surface. At one time, there was a northern hemisphere ocean as much as a mile deep. Planetary scientists now agree that there was a global or near-global flood on Mars, where liquid water, if it exists at all, is extremely rare today. Yet these same scientists would scoff at the idea that there once was a global Flood on Earth, a planet awash in water.

Given that liquid water once was abundant on Mars, it should be no surprise that at least a few vestiges of that largess may still exist in cloistered corners of Mars. At least such a thing is possible in a worldview where Mars is only thousands of years old, not billions of years. Planetary scientists generally think that Mars has been dry for two billion years or more. The question is, could significant liquid water have survived since this time?

Even if remnants of liquid water exist on Mars today, that does not prove that life once existed or exists on Mars today. Furthermore, even if bacteria were found on Mars today or it were shown that bacteria existed on Mars in the past, that would not prove that evolution occurred there, any more than the existence of bacteria on the earth proves that evolution has occurred here. All such a discovery would prove is that bacteria either existed in the past or now exist on Mars. No one has ever observed the spontaneous generation of bacteria or the evolution of bacteria into something else. Besides, bacteria are a long way from conscious, intelligent life. The continued hype about water and possible life on Mars is all wishful thinking of evolutionists desperate for some evidence that the evolution of life has occurred somewhere.

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